Mailing machines including postage metering systems are known in the art including the DM SERIES of mailing machines available from Pitney Bowes Inc. of Stamford, Conn. A postage metering system applies evidence of postage, commonly referred to as postal indicia, to an envelope or other mailpiece (directly or on a label to be applied thereto) and accounts for the value of the postage dispensed. The postage metering systems typically employ a red fluorescent ink to imprint a postage indicium although it is not the only color used. If a colored envelope is used for a mail piece, there may not be sufficient contrast from the indicium.
For example, during the end of year holiday season, it is common for business to send greeting cards to customers and colleagues. Such cards may not have white envelopes but may be processed by a company mailroom employee using a postage meter to apply postage. A typical postage meter utilizes. Such an indicium might not have significant contrast from the envelope and might not be easily read optically by a mail processing/sorting machine or by the naked eye. Additionally, during the Valentine's Day holiday in the United States, many greeting cards are mailed in colored envelopes such as pink or red envelopes. The sender may use a postage meter for postage payment. However, the user might intend to utilize a stamp but might then have the mailpiece collected by a mail aggregator service that would then apply a postage indicium. Accordingly, since more mail is being aggregated, it is more likely that a postage indicium will be applied to an envelope and readability contrast may become a problem in mail processing/sorting.
Thermochromic compositions of color formers and Lewis acids have been described such as in U.S. Pat. No. 6,908,505 B2, issued Jun. 21, 2005 that describes a two-layer reversible thermochromic system printed over a substrate and that transition from colorless to a colored state. One of the challenges that mailing machine manufactures and mail processing entities have is that they must deal with many different types of envelopes. For example, in the United States, the Unites States Postal Service (USPS) mandates certain physical characteristics of mail in the Domestic Mail Manual (DMM). However, a wide range of media types may be used for envelope substrates.
As barcode use becomes more widespread on mail pieces to facilitate the use of value added services and postage revenue security schemes it is imperative that these barcodes are machine readable with optical sensors such as the USPS Wide Field of View camera (WFOV). To insure barcode readability, flat, light-colored backgrounds may advantageously be used. The USPS might even decide to limit the customer's envelope use to the types that enable readability or have the user print indicia on controlled stock such as labels that are then adhered to the mailpiece. Both of those solutions have disadvantages including adding extra cost to the mailings and by limiting the advertising that can be done.
Accordingly, there is a need for a machine readable colored envelope that is easily processed by mail processing/sorting equipment. Additionally, there is a need for a system and method for processing reversible photochromic colored envelopes in mail processing/sorting systems including reversible “negative photochromatic” colorants. Furthermore, there is a need for a system and method for processing a single layer indicium printing on a reversible thermochromic colored envelope in mail processing/sorting systems.